The Distance Travelled from Rest to Terminal Velocity by a Sphere in Air

The distance travelled as a function of velocity for falling spherical drops starting from rest was calculated. This was done for 1 to 5 millimeter spheres to determine the travel distance required for designing experiments where velocities approaching terminal are required. The results showed that 80 percent of terminal velocity is reached after spheres of unit density and diameter of 5 millimeters have fallen from rest through a distance of 7.5 meters. To achieve 85 percent of terminal velocity, an increase of only 5 percent, 9.5 meters is required. Also calculated was the velocity of particles blown upward from rest in a vertical airstream. This was done to provide information for comparison of experimental to theoretical results on the effect of dust on aerodynamic drag.